Assiqnob to the stztt ignition comfany



Jan. 27, 193 D. scHAAF SEAL FOR SPARK PLUGS Filed May 1'7, 1929 3mxnbrDOWNS SGHAAF G Patented Jan. 27, 1931 UNITED STATES PATENT OFFICE- DOWNBSCELAI', OF OOLUKBUS, OHIO, ASSIGNOR TO THE STI'IT IGNITION comm, I OFCOLUMBUS, OHIO, A CORPORATION 01' OHIO smnroa srnzax rnues Applicationfiled Kay 17, 1929. Serial No. 863,770.

According to the common practice at present the battery or generatorelectrode of a spark plug is mounted in a porcelain insulator, thesealing between the electrode and theinsulator being effected by meansof a cement of silica and silicate of soda. The cement referred tocontains more orless water and such a sealing is not uniformlysuccessful because of the creepa e of the cement anda resultant leakage0% cylinder gases and crackin of the porcelain.

It is therefore, t e aim of this invention to provide a seal that shallnot be subject to such objections. Because the metal bismuth has theproperty of expanding when changed from a liquid to a solid state andbecause the melting point of that metal is 518 Fah. and such temperatureis not reached in the porcelain insulator of a spark plug at the exposedportionwhere the seal is to be applied I use that metal or a suitablealloy thereof to effect the sealing.

In the accompanying drawings Figure 1 is a sectional view of the shellof a spark plug with the porcelain insulator containing my improvementshown in full. p, Fig. 2 is a sectional view of the porcelain insulatorshowing my seal applied to the electrode wire.

In the views 5 designates the metallic shell which is of ordinary formand construction; 6 the porcelain insulator, and 7' the electrode wire,the latter bein provided with an enlarged and threadetf end for theelectrical connections.

On the electrode wire 7 just below the threaded end thereof I moldasleeve 8 of bismuth or a suitable alloy of bismuth. This molding iseffected by pouring the molten bismuth or an alloy thereof into theinsulator while the electrode is positioned therein.

The porcelain,-\in the instance shown is at its upper end and beforebaking formed with an internal threaded socket of larger diameter thanthe diameter of the wire of the electrode and into this socket aroundthe wire the bismuth or alloy thereof is poured as before stated.However the seal may be ap lied inother obvious ways. The wire I at t eportion' wherethe seal is applied is roughenedor ment.

Particular advantages, among others, of a metallic seal such asdescribed is that, first, it is gas'tight as compared with a ceramicseal, second, it remains in the position applied whereas a ceramic sealsuch as referred to creeps toward the nose of the insulator and onexpansion at such point of the seal often causes cracking oftheinsulator, third, economy of time and labor in manufacture of theseal.

A further decided advantage of bismuth as compared with the cement asthe sealing material is that the metal has no corrosive effect whereaswith cement the wire is sometimes destroyed and rendered useless by thecorrosive action of the cement.

The' forms and assembling of the parts can be changed without departingfrom the gist of the/invention as claimed.

What I claim is:

1. The combination of a spark plug whose electrode and insulator aresecured in gas tight relation by a bismuth seal.

2. The combination of a spark plug whose electrode and insulator aresecured in gas tight relation by a bismuth seal located in ing ofbismuth or an alloy thereof that ex- 1 pands on solidification.

DOWNS SCHAAF.

